A number of therapeutic concepts are currently used in the treatment of tumors. Apart from using surgery, chemotherapy and radiotherapy are predominant. All these techniques are, however, associated with considerable side effects. The use of replication selective oncolytic viruses provides for a new platform for the treatment of tumors. In connection therewith a selective intra-tumor replication of a viral agent is initiated which results in virus replication, lysis of the infected tumor cell and spreading of the virus to adjacent tumor cells. As the replication capabilities of the virus is limited to tumor cells, normal tissue is spared from replication, and thus from lysis by the virus.
For the time being, several viral systems are subject to clinic trials aiming at tumor lysis. One example for such an adenovirus is dl1520 (Onyx-015), which has been successfully used in clinical phases I and II (Khuri, F. et al. Nature Medicine 6, 879-885, 2000). Onyx-015 is an adenovirus having a completely deleted E1B-55kDa gene. The complete deletion of the E1B55kDa protein of the adenovirus is based on the discovery that replication, and thus lysis of cells, is possible with an adenoviral vector which has a p53 deficiency (Kirn, D. et al., Proc. Am. Soc. Clin. Oncol. 17, 391a, 1998), whereby normal cells are not harmed. More particularly, the E1B-55kDa gene product is involved in the inhibition of p53, the transport of viral mRNA and the switching off of the protein synthesis of the host cell. The inhibition of p53 occurs via formation of a complex consisting of p53 and the adenoviral encoded E1B-55kDa protein and/or a complex consisting of E1B-55kDa and E4orf6, p53, coded by TP53, is the starting point for a complex regulatory mechanism (Zambetti, G. P. et al., FASEB J. 7, 855-865, 1993), which results, among others, in an efficient inhibition of the cellular replication of viruses like adenovirus. The gene TP 53 is deleted or mutated in about 50% of all human tumors, which results in the absence of desired apoptosis due to chemotherapy or radiation therapy, resulting in an usually unsuccessful tumor treatment.
A further concept of tumorlytic adenoviruses is based on the discovery that if the E1A protein is present in a specific deleted form or comprises one or several mutations, which do not affect the binding of Rb/E2F and/or p107/E2F and/or p130/E2F, such adenovirus will not induce the entry of the infected cells into the S phase and will be capable of replicating in tumor cells which do not have a functional Rb protein. Additionally, the E1A protein can be deleted at the N-terminus and comprises one or several mutations in the region of amino acid positions 1 to 76 of the E1A proteins, respectively, in order to inhibit the binding of E1A to p300, and thus to provide for a more selective replication in tumor cells. These approaches are described in an exemplary manner in European patent EP 0 931 830. Examples for such viruses are AdΔ24, dl922-947, E1Ad/01/07 and CB016 (Howe, J. A. et al., Molecular Therapy 2, 485-495, 2000; Fueyo, J. et al., Oncogene 19, 2-12, 2000; Heise, C. et al., Nature Medicine 6, 11341139, 2001; Balague, C. et al., J. Virol. 75, 7602-7611, 2001). These adenoviral systems for oncolysis known in the prior art thus comprise distinct deletions in the E1A protein, whereby such deletions had been made under the assumption that a functional Rb protein and complexes consisting of inactive Rb protein and E2F, respectively, would block an efficient in vivo replication, and in order to provide an adenoviral replication in vivo in Rb-negative/mutated cells only. These adenoviral systems, according to the prior art, are based on E1A in order to control in vivo replication by means of the early E2 promoter (engl. E2 early promoter) and free E2F (Dyson, N. Genes & Development, 12, 2245-2262, 1998).
A further form of tumorlytic adenoviral systems is based on the use of selective promoters for specifically expressing the viral oncogene E1A, which provides for a selective replication in tumor cells (Rodriguez, R. et al., Cancer Res. 57, 2259-2563, 1997).
As described above, the selection of a cellular background which is appropriate for the respective concept underlying the mode of action is important for the various concepts of adenoviral tumorlytic viruses. In other words, the various adenoviral systems currently known may only be used if distinct molecular biological prerequisites are realized. This limits the use of such systems to distinct patient groups.
A particular problem in the treatment of tumor diseases arises once the patients develop a so-called multidrug resistance (engl. multidrug resistance (MDR)), which represents a particularly well-studied form of resistance of tumors against cytostatics (Gottesman and Pastan, Annu. Rev. Biochem. 62, 385-427, 1993). It is based on the overexpression of the membrane-bound transport protein P-glycoprotein, which belongs to the so-called ABC transporters (Stein, J. et al., JBC 276, 28562-69, 2001, J. Wijnholds, Novartis Found Symp., 243, 69-79, 2002). Bargou, R. C. et al. and Oda, Y. et al (Bargou, R. C. et al., Nature Medicine 3, 447-450, 1997; Clin. Cancer Res. 4, 2273-2277, 1998) which were able to show that nuclear localisation of the human transcription factor YB-1 is directly involved in the activation of the expression of the P-glycoprotein. Further studies confirmed that YB-1 is transported into the nucleus by various stress conditions such as UV irradiation, administration of cytostatics (Koike, K. et al., FEBS Lett 17, 390-394, 1997) and hyperthermia (Stein, U. et al., JBC 276, 28562-69, 2001). Further studies confirmed that the nuclear localisation of YB-1 has an impact on one further ABC transporter. This ABC transporter is referred to as MRP (engl. multidrug resistance-related protein) and is involved in the formation of the so-called atypical non-P-glycoprotein dependent multidrug resistance (Stein, U. et al., JBC 276, 28562-69, 2001).
The problem underlying the present invention is to provide a technical teaching, and in particular, a means which allows to treat an organism, more particularly to human organism and a group of patients, respectively, specifically with tumorlytically active agents. It is a further problem underlying the present invention to provide a means which is suitable to cause tumorlysis in patients having tumor diseases which are resistant to cytostatics, particularly those which have a multidrug resistance. Finally, a problem underlying the present invention is to provide for an adenovirus which is suitable for cell lysis.